Device for absorbing floor-landing shock for legged mobile robot

ABSTRACT

A landing shock absorbing device  18  disposed in a foot mechanism  6  of a leg of a robot, wherein an inflatable bag-like member  19  (a variable capacity element) is provided at a ground-contacting face side of the foot mechanism  6.  The bag-like member  19  is constructed of an elastic material such as rubber and has a restoring force. An interior portion of the bag-like member  19  is communicated with the atmosphere side through a flow passage  20.  During a landing motion of the leg, the bag-like member  19  makes contact with the ground to be compressed, and the air in the interior portion thereof flows out into the atmosphere through the flow passage  20,  so that its outflow resistance is generated. Accordingly, a landing shock is reduced. In a lifting state of the leg, the restoring force of the bag-like member  19  allows the bag-like member  19  to be inflated while the air flows into the interior portion thereof. An impact load during the landing of the leg of the legged mobile robot may smoothly be reduced in a light-weight configuration.

TECHNICAL FIELD

The present invention relates to a landing shock absorber for reducingan impact load during a landing motion of a leg of a legged mobilerobot.

BACKGROUND ART

In a legged mobile robot such as a biped mobile robot equipped with aplurality of legs, each leg is brought into contact with a floor througha ground-contacting face portion of a foot mechanism provided on a farend portion thereof. More particularly, the foot mechanism is amechanism connected to a joint on the farthest end side of each leg (anankle joint). The legged mobile robot moves by lifting and landingmotions of each leg. More particularly, the lifting and landing motionsare a repetition of motions that while at least one leg of a pluralityof legs as a supporting leg maintains a foot mechanism of the supportingleg in a ground-contacting state, the other leg as a free leg lifts afoot mechanism of the free leg from its ground-contacting location intothe air and moves the same, and make contact with the ground on otherground-contacting location.

In such a legged mobile robot, when a ground-contacting face portion ofa foot mechanism of the leg is brouhgt into contact with the ground bythe landing motion of each leg, a relatively great impact load (atransient floor reaction force) instantaneously acts through the footmechanism of the leg. Particularly, when the legged mobile robot ismoved at relatively high moving speed, motion energy of the leg inmoments immediately before the foot mechanism of the leg makes contactwith the ground is great, so that the impact load will be high. Whenthis impact load is high, rigidity of each portion of each leg needs tobe enhanced in order to resist the load, and furthermore, this willinterfere with a size reduction and a weight reduction of each leg.Accordingly, a reduction (shock absorption) of such an impact load isdesired.

As such a shock absorber, for example, the one that the presentapplicant proposed in Japanese Patent Laid-Open Publication No.5-305578is known. In this shock absorber, a cylinder filled with hydraulic oilis provided at a heel of the foot mechanism, and a rod is extendedlyprovided from a piston slidable in this cylinder toward a bottom faceside of the heel of the foot mechanism. A ground-contacting elementwidened in diameter in a mushroom shape is provided on a tip portion ofthe rod. Additionally, the piston is energized in a direction that theground-contacting element projects to the bottom face side of the footmechanism by a spring accommodated in the cylinder on the upper sidethereof. Furthermore, in the piston, a flow passage that allows thehydraulic oil to flow between an upper chamber and a lower chamberthereof is drilled.

In the shock absorber configured in this manner, at the time of thelanding motion of the leg, the aforementioned ground-contacting elementmakes contact with the ground and is pressed with the piston in adirection opposite to an energizing force of the spring. At this moment,while the hydraulic oil in the cylinder flows through the flow passageof the piston, the piston slides in a direction that the pistoncompresses the spring, and this allows the impact load during thelanding motion of the leg to be reduced.

However, in the shock absorber, as a result of the use of the hydraulicoil, particularly, when a moving speed of a robot is fast, pressure ofthe hydraulic oil suddenly increases at the instant when theground-contacting element touches the ground. Accordingly, a relativelyhigh impact load tends to be generated at the instant when theground-contacting element touches the ground. In this situation, when anarea of an aperture of the flow passage of the piston is designed to berelatively large, the sudden increase in the pressure of the hydraulicoil at the instant when the ground-contacting element touches the groundmay be controlled. However, in a situation like this, a damping effectcaused by a flow of the hydraulic oil (an attenuating effect of motionenergy) decreases and a vibration of a floor reaction force immediatelyafter the landing motion of the foot mechanism tends to be generated,and resultingly, a posture of the robot tends to be unstable.

Furthermore, in the shock absorber, as a result of the use of thehydraulic oil, weight of the shock absorber will be heavy, resulting ininterfering with a weight reduction of the robot. Additionally, theground-contacting element that makes contact with the ground during thelanding motion of the leg can only move in a sliding direction of thepiston (an axial center direction of the cylinder) and is a solid body.Consequently, the impact load acting on the ground-contacting elementmay act in a direction that crosses a movable direction thereofdepending on a geometry of a floor, so that the impact load may notadequately be reduced, and a damage of the shock absorber may begenerated.

In light of such a background, it is an object of the present inventionto provide a landing shock absorber that can smoothly reduce an impactload during a landing motion of a leg of a legged mobile robot with alight-weight configuration.

DESCLOSURE OF INVENTION

To achieve such an object, a landing shock absorbing device of a leggedmobile robot of the present invention is characterized in that in thelegged mobile robot moving through a ground-contacting face portion of afoot mechanism by lifting and landing motions of a plurality of legsthat can make contact with the ground, respectively, a variable capacityelement provided in the foot mechanism of the leg to be compressed byundergoing a floor reaction force during the landing motion of each legand to be inflatable when no longer undergoing the floor reaction forceat least by the lifting motion of the leg, thereby allowing compressiblefluid to flow into and flow out of an interior portion thereof with theinflation and the compression thereof, and an inflow/outflow means forflowing the compressible fluid into the variable capacity element whileinflating the variable capacity element in a lifting state of each legand flowing the compressible fluid out of the variable capacity elementwith the compression of the variable capacity element caused by thefloor reaction force are provided, and outflow resistance is generatedduring the outflow of the compressible fluid from the variable capacityelement by the inflow/outflow means (a first invention).

Further, in the present invention, the landing motion of each legdenotes a motion for moving down the foot mechanism to allow theground-contacting face portion to make contact with a floor from a statethat the ground-contacting face portion of the foot mechanism of the legis lifted from the floor, and the lifting motion of each leg denotes amotion for lifting the foot mechanism into the air to remove theground-contacting face portion from the floor from a state that theground-contacting face portion of the foot mechanism of the leg is putin contact with the floor. Additionally, the lifting state of each legor the foot mechanism denotes a state that the entire ground-contactingface portion of the foot mechanism of the leg is removed from the floor.Moreover, the landing state of each leg or the foot mechanism denotes astate that the entire or a partial ground-contacting face portion of thefoot mechanism of the leg is put in contact with the floor.

According to the present invention (the first invention), during thelanding motion of each leg, the variable capacity element in an inflatedstate is compressed with the compressible fluid in the interior portionthereof, and resultingly, pressure of the compressible fluid increases.At this time, the pressured compressible fluid in the variable capacityelement flows out of the variable capacity element with the outflowresistance by the inflow/outflow means. This allows motion energy of theleg to be attenuated. Additionally, in this situation, some of themotion energy of the leg is transformed to elastic energy of thecompressible fluid to be absorbed by a spring property of thecompressible fluid, and furthermore, the elastic energy is dissipated bythe outflow resistance of the compressible fluid from the variablecapacity element. While such an operation prevents a generation of aninstantaneous sudden change of the floor reaction force acting on theleg through the variable capacity element and the compressible fluid inthe interior portion thereof, the impact load acting on the leg duringthe landing motion of the leg (the transient floor reaction force) isreduced. Therefore, according to the present invention, the impact loadat the time of the landing of the leg may smoothly be reduced and a goodshock absorbing effect may be obtained.

Further, as the compressible fluid, gas such as air, fluid or gelcontaining bubbles, etc., are included. In this situation, particularly,when the gas as the compressible fluid is used, the compressible fluidwill be light weight and then the landing shock absorbing device of thepresent invention may be light weight.

In the present invention (the first invention), the variable capacityelement may be provided on a bottom face side of the foot mechanism ofthe leg to make contact with the ground ahead of the ground-contactingface portion of the foot mechanism of the leg during the landing motionof each leg, or may be placed between the ground-contacting face portionand a joint connected to the foot mechanism (an ankle joint).

More particularly, when the variable capacity element is provided on thebottom face side of the foot mechanism to make contact with the groundahead of the ground-contacting face portion of the foot mechanism of theleg during the landing motion of each leg, the variable capacity elementis preferably constructed of a deformable bag-like member (a secondinvention). In other words, the bag-like member makes contact with theground ahead of the ground-contacting face portion of the foot mechanismof the leg to be compressed during the landing motion of each leg. Atthis moment, the bag-like member can be deformed to meet a surfacegeometry of the floor, resulting in exerting a shock absorbing functionof the landing shock absorbing device of the present invention withoutdepending on a floor shape or the like as long as the bag-like membercan make contact with the ground. Consequently, certainty of an impactload reducing effect during the landing of the leg may be enhanced.Additionally, the bag-like member has a high degree of flexibility inthe deformation, and hence, even when the floor reaction force acts onthe bag-like member from various directions during the landing of eachleg, such a situation that the bag-like member is damaged may beavoided.

In the present invention that the variable capacity element isconstructed of the bag-like member like this (the second invention), thebag-like member is preferably constructed by using an elastic materialto have a restoring force toward an inflating direction thereof (a thirdinvention). That is to say, when the bag-like member itself does nothave the restoring force toward the inflating direction thereof, inorder to inflate the bag-like member before the landing motion of eachleg, it is necessary to actively supply the compressible fluid into thebag-like member by a fluid supplying device, or energize the bag-likemember in the inflating direction by a spring or the like different fromthe bag-like member. Consequently, components needed for the landingshock absorbing device tends to be increased. On the contrary, when thebag-like member itself has the restoring force toward the inflatingdirection thereof, the bag-like member can suck in the externalcompressible fluid while inflating by the restoring force thereof, sothat its configuration may be simplified by reducing components of thelanding shock absorbing device. Particularly, when the air is used asthe compressible fluid to carry out inflow and outflow of the airbetween the bag-like member and the atmosphere, for example, a tank orthe like for storing the compressible fluid supplied to the bag-likemember will not be needed, either.

Additionally, in the second invention or the third invention, aplurality of the bag-like members are preferably provided (a fourthinvention). Accordingly, during the landing motion of the leg, at leastone bag-like member may surely be put into contact with the ground toreduce the impact load without depending on a geometry of a floor or thelike.

Furthermore, in the second through the fourth inventions, a porouselement (for example, a sponge) inflatable together with the bag-likemember is preferably accommodated in an interior portion of the bag-likemember (a fifth invention). Accordingly, at the time of the compressionof the Bag-like member, outflow resistance is generated when thecompressible fluid that is entered into holes of the inflatable porouselement flows out to an external portion of the holes, and hence, adamping effect of the landing shock absorbing device may be enhanced incooperation with outflow resistance of the compressible fluid in thebag-like member by the inflow/outflow means.

Additionally, in the present invention (the first through the fifthinventions), the inflow/outflow means is preferably configured in such amanner that inflow resistance of the compressible fluid into thevariable capacity element is lower than outflow resistance of thecompressible fluid from the variable capacity element (a sixthinvention). In other words, the inflow resistance of the compressiblefluid into the variable capacity element is lowered, thereby allowingthe compressible fluid to quickly flow into the variable capacityelement to inflate the variable capacity element in a short time.Accordingly, a situation that the variable capacity element isinadequately inflated may be prevented before the landing of each leg,and then the impact load at the time of the landing motion may properlybe reduced. Moreover, the inflow resistance is lowered, thereby reducingenergy loss when the variable capacity element is inflated, so that heatmay be controlled. In addition, the outflow resistance is increased,thereby allowing the damping effect of the landing shock absorbingdevice (an attenuating effect of motion energy) to be enhanced, andresultingly, the floor reaction force acting on the leg may be put intoa steady state at an early stage.

Additionally, in the present invention (the first through the sixthinvention), the inflow/outflow means is preferably provided with upperlimit pressure limiting means for limiting pressure in the variablecapacity element to no higher than a predetermined upper limit pressure(a seventh invention). Accordingly, when the variable capacity elementis compressed during the landing motion of each leg, the pressure in thevariable capacity element instantaneously becomes excessively high, andresultingly, a situation that a great force contrarily acts on the legfrom the compressible fluid in the variable capacity element may beprevented. Moreover, a situation that the variable capacity element isdamaged by excessive pressure can also be prevented by limiting theupper limit of the pressure in the variable capacity element. Further,the upper limit pressure limiting means may be configured by a reliefvalve connected to the variable capacity element, for example.

In this manner, in the present invention provided with the upper limitpressure limiting means (the seventh invention), the upper limitlimiting means is preferably disposed in a manner that the upper limitpressure can variably be adjusted (an eighth invention). Accordingly,the upper limit of the pressure of the compressible fluid in thevariable capacity element at the time of the landing motion of the legmay be adjusted depending on a moving pattern of the robot and the like,so that the shock absorbing effect in response to the moving pattern ofthe robot and the like may be given. Further, in general, as the movingspeed of the robot increases, an impact load at the time of the landingof each leg tends to be high. Consequently, in order to effectivelyreduce the impact load, the upper limit pressure is preferably adjustedto increase the upper limit pressure as the moving speed of the robotincreases.

Additionally, in the present invention (the first through the eighthinventions), the inflow/outflow means is preferably disposed in a mannerthat the outflow resistance of the compressible fluid from the variablecapacity element can variably be adjusted (a ninth invention).Accordingly, a characteristic of the variation of the pressure of thecompressible fluid in the variable capacity element at the time of thelanding motion of the leg may be adjusted depending on the movingpattern of the robot and the like. Further, in general, as the movingspeed of the robot increases, an impact load at the time of the landingof each leg tends to be high. Consequently, in order to effectivelyreduce the impact load, the outflow resistance is preferably increasedas the moving speed of the robot increases. In addition, the adjustmentof the outflow resistance can be performed by providing a variablethrottle valve such as a solenoid proportional valve in a passage forflowing the compressible fluid out of the variable capacity element.

Additionally, in the present invention (the first through the ninthinvention), the inflow/outflow means may flow the compressible fluid outof the variable capacity element and flow the compressible fluid intothe variable capacity element through respectively independent flowpassages, but preferably performs through a common flow passagecommunicated with the variable capacity element (a tenth invention).Accordingly, a configuration of the inflow/outflow means may besimplified. Further, a flow passage for flowing the compressible fluidinto the variable capacity element and a flow passage for flowing thecompressible fluid out of the variable capacity element do not need tobe entirely common, but may also be partially common (a part of a pathof the flow passages). Additionally, valves such as check valves or thelike may also be disposed in these flow passages as needed.

Additionally, in the present invention (the first through the tenthinvention), the compressible fluid is a gas and the inflow/outflow meansis preferably provided with means for increasing pressure in thevariable capacity element in an inflated state of the variable capacityelement to be higher than atmospheric pressure (an eleventh invention).Accordingly, the pressure of the compressible fluid in the variablecapacity element will be high during the landing motion of each leg,thereby allowing the outflow resistance of the compressible fluid to beenhanced, and consequently, the damping effect of the landing shockabsorbing device of the present invention may be enhanced. In addition,when the variable capacity element itself does not have a restoringforce toward an inflating direction, or even when means such as a springfor energizing the variable capacity element in the inflating directionis not provided, the variable capacity element may be inflated by aninflow of a gas as the compressible fluid into the variable capacityelement.

In such a manner, in the present invention (the eleventh invention) thatthe pressure in the variable capacity element in the inflated state isadapted to be higher than the atmospheric pressure, means for limiting acapacity of the variable capacity element in the inflated state to nomore than a predetermined upper limit capacity is preferably provided (atwelfth invention). Accordingly, in a state that the variable capacityelement is inflated up to the upper limit capacity, preload will begiven to the variable capacity element according to a pressuredifference between the pressure in the variable capacity element and theatmospheric pressure. Consequently, during the landing motion of eachleg, the pressure in the variable capacity element rises rapidly, and asa result, a peak of the impact load at the time of landing may becontrolled to be low. Therefore, the impact load reducing effect may beenhanced.

Further, limitation of the upper limit capacity of the variable capacityelement can be done, for example by preventing the variable capacityelement from inflating over the upper limit capacity by mechanical meansor electromagnetic means, or shutting off the flow passage for flowingthe compressible fluid into the variable capacity element when thevariable capacity element reaches the upper limit capacity by a valve.

Additionally, in the present invention (the first through the twelfthinventions), the compressible fluid is assumed to be the air and theinflow/outflow means is preferably provided with means for flowing outthe air in the variable capacity element to the atmosphere when thevariable capacity element is compressed, and flowing the air in theatmosphere into the variable capacity element when the variable capacityelement is inflated (a thirteenth invention). Accordingly, the tank orthe like for storing the compressible fluid will not be needed, and whenthe air flows into and out of the variable capacity element, heatgenerated by the inflow resistance and the outflow resistance can bereleased into the atmosphere. As a result, a situation that heat isstored in the variable capacity element and the air in the interiorportion thereof may be prevented. Furthermore, a damping characteristicof the landing shock absorbing device or the like may be stabilized.

Additionally, the present invention (the fist through the thirteenthinventions) is preferred when the legged mobile robot is a robot that aposition and a posture of the foot mechanism is controlled by compliancecontrol so as to allow a moment about an axis in a horizontal directionfor the floor reaction force acting on the foot mechanism of each leg(for example, a moment detected by a six-axis force sensor or the like)to follow a predetermined desired moment (a fourteenth invention). Thatis to say, a spring constant of the compressible fluid is decreased bythe pressure of the variable capacity element according to the landingmotion of the leg, and consequently, a gain of the control (a compliancegain) may be enhanced, while ensuring stability of a control system forthe compliance control. As a result, a following-property of a momentabout the axis in the horizontal direction acting on each foot mechanismto the desired moment may be enhanced. Consequently, the stability ofthe posture of the robot may be ensured, while properly reducing theimpact load at the time of the landing. Additionally, in particular, inthe aforementioned fourth invention provided with multiple bag-likemembers, when the compliance control is performed, the moment about theaxis in the horizontal direction may be acted on each foot mechanism bya ground contact for any of multiple bag-like members during the landingmotion of the leg. Consequently, the stability of the posture of therobot may effectively be ensured by the above compliance control, sothat the floor reaction force acting on the leg may be put into a steadystate at an early stage.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view showing a basic configuration of a legged mobilerobot in an embodiment of the present invention,

FIG. 2 is a cross sectional view showing a side face of a foot mechanismprovided with a landing shock absorbing device of a first embodiment ofthe present invention,

FIG. 3 is a plan view viewed from a bottom face side of the footmechanism of FIG. 2,

FIG. 4 is a flowchart showing processing for a motion control of thelegged mobile robot of FIG. 1, and

FIG. 5 is a schematic diagram describing an operation of the landingshock absorbing device of the foot mechanism of FIG. 2.

FIG. 6 is a cross sectional view showing a side face of a foot mechanismequipped with a landing shock absorbing device of a second embodiment ofthe present invention,

FIG. 7 is a cross sectional view showing a configuration ofinflow/outflow means of a landing shock absorbing device of a thirdembodiment of the present invention,

FIG. 8 is a schematic diagram of substantial portions of a footmechanism equipped with a landing shock absorbing device of a fourthembodiment of the present invention,

FIG. 9 is a schematic diagram of substantial portions of a footmechanism equipped with a landing shock absorbing device of a fifthembodiment of the present invention, and

FIG. 10 is a schematic diagram of substantial portions of a footmechanism equipped with a landing shock absorbing device of a sixthembodiment of the present invention.

FIG. 11 is a schematic diagram of substantial portions of a footmechanism equipped with a landing shock absorbing device of a seventhembodiment of the present invention,

FIG. 12 is a schematic diagram of substantial portions of a footmechanism equipped with a landing shock absorbing device of a eighthembodiment of the present invention,

FIG. 13 is a diagram for describing an operation of the landing shockabsorbing device of the eighth embodiment,

FIG. 14 is a schematic diagram of substantial portions of a footmechanism equipped with a landing shock absorbing device of a ninthembodiment of the present invention, and

FIG. 15 is a schematic diagram of substantial portions of a footmechanism equipped with a landing shock absorbing device of a tenthembodiment of the present invention.

FIG. 16 is a schematic diagram of substantial portions of a footmechanism equipped with a landing shock absorbing device of a eleventhembodiment of the present invention,

FIG. 17 is a flowchart showing control processing of inflow/outflowmeans of a landing shock absorbing device of the eleventh the presentinvention,

FIG. 18 is a cross sectional view showing a side face of a footmechanism equipped with a landing shock absorbing device of a twelfthembodiment of the present invention,

FIG. 19 is a cross sectional view showing a side face of substantialportions of a foot mechanism equipped with a landing shock absorbingdevice of a thirteenth embodiment of the present invention, and

FIG. 20 is a plan view showing an arrangement configuration for abag-like member of the landing shock absorbing device of a fourteenthembodiment of the present invention.

BEST MODE OF CARRYING OUT THE INVENTION

Referring to FIGS. 1 through 5, a first embodiment of the presentinvention is described. FIG. 1 is a side view showing an overall basicconfiguration of a legged mobile robot 1 of the present embodiment inschematic form. As shown in FIG. 1, for example, the legged mobile robot1 of the present embodiment is a biped mobile robot comprising a pair of(two) legs 3, 3 extendedly disposed from a lower end portion of itsupper body 2 (torso). Further, arms and a head may be attached on theupper body 2.

Each leg 3 is constructed by connecting a thigh 4, a lower leg 5, and afoot mechanism 6 in the order listed through a hip joint 7, a knee joint8, and an ankle joint 9 from the lower end portion of the upper body 2.More specifically, each leg 3 is adapted to be configured with the thigh4 extendedly disposed from the lower end portion of the upper body 2through the hip joint 7, the lower leg 5 connected to a far end portionof the thigh 4 through the knee joint 8, and the foot mechanism 6connected to a far end portion of the lower leg 5 through the anklejoint 9. Each leg 3 can be brought into contact with a floor A throughthe foot mechanism 6 presented on a distal end side thereof, andsupports the upper body 2 by this ground-contact. In this situation, thehip joint 7 of each leg 3 is adapted to be capable of rotary motionsabout three axes in an upward/downward direction, a forward/backwarddirection, and a right/left direction, the knee joint 8 is adapted to becapable of a rotary motion about one axis in the right/left direction,and the ankle joint 9 is adapted to be capable of rotary motions of twoaxis in the forward/backward direction and the right/left direction ofthe robot 1. According to the rotary motions of respective joints 7through 9, each leg 3 is adapted to be capable of performing a movementsubstantially the same as a human leg.

Additionally, the respective joints 7 through 9 of each leg 3 isprovided with an electric motor (not shown) as an actuator forperforming the rotary motion about each axis. Furthermore, the upperbody 2 of the robot 1 is equipped with a controller 10 for controllingmotions of the legs 3, 3 of the robot 1 (a motion control for theelectric motor of the respective joints 7 through 9), and a battery 11as an electric source for a motion of the robot 1, etc. The controller10 is constructed of an electric circuit including a microcomputer, etc.In this situation, in moving the robot 1, the controller 10 attempts tomove the robot 1 like a human by alternately repeating a lifting and alanding motions for the two legs 3, 3. More specifically, a repetitionof the lifting and landing motions is an action as follows. In otherwords, either one of the two legs 3, 3 is taken as a supporting leg andthe other as a free leg. In a state that the foot mechanism 6 of the leg3 on a supporting leg side is landed on the floor A, the foot mechanism6 of the leg 3 on a free leg side is lifted from the floor A into theair. Furthermore, the foot mechanism 6 of the leg 3 on the free leg sideis moved in the air, and then landed on a desired place. The landed leg3 on the free leg side is, then, newly taken as the supporting leg andthe leg 3 which has been taken as the supporting leg is newly taken asthe free leg, and the leg 3 newly taken as the free leg is moved asdescribed above. Such a repetition of the motion of the legs 3, 3 is therepetition of the lifting and landing motions of the legs 3, 3 duringthe movement of the robot 1.

Referring to FIG. 2 and FIG. 3, a configuration of the foot mechanism 6of each leg 3 is further described. FIG. 2 is a cross sectional viewshowing a side face of the foot mechanism 6, and FIG. 3 is a plan viewviewed from a bottom face side of the foot mechanism 6.

The foot mechanism 6 is provided with a foot plate member 12 in agenerally tabular form as a skeletal member. The foot plate member 12 isdesigned with its front end portion (toe portion) and its rear endportion (heel portion) each curved slightly upward, but otherwise in aflat tabular form. In addition, on a top face portion of the foot platemember 12, a tube member 13 in a cross sectionally rectangular form isfixedly installed with its axis in a vertical direction. In an interiorportion of the tube member 13, a movable plate 14, which is disposed tobe movable substantially in the vertical direction to be arranged alongan inner circumferential surface of the tube member 13, is provided andthe movable plate 14 is connected to the ankle joint 9 through asix-axis force sensor 15. The six-axis force sensor 15 detects a floorreaction force acting on the foot mechanism 6 (specifically, atranslational force of three axis directions in a forward/backwarddirection, a right/left direction, and an upward/downward direction, andmoment about three axes), and its detected output is input into thecontroller 10.

Additionally, the movable plate 14 is connected to the top face portionof the foot plate member 12 through a plurality of elastic members 16(described as a spring in FIG. 2) with a peripheral portion of its lowerface constructed of a spring, rubber, or the like. Therefore, the footplate member 12 is connected to the ankle joint 9 through the elasticmember 16, the movable plate 14 and the six-axis force sensor 15.Further, the interior portion of the tube member 13 (a space under themovable plate 14) is opened to an atmospheric side through a hole or agap which is not shown, so that the air in the atmosphere can freelycome into and go out of the interior portion of the tube member 13.

Ground-contacting members 17 are attached to the bottom face (the lowerface) of the foot plate member 12. The ground-contacting members 17 areelastic members intervened between the foot plate member 12 and thefloor in a state that the foot mechanism 6 is landed (an elastic memberthat. directly makes contact with the floor), and fixed to four cornersof the ground-contacting surface of the foot plate member 12 (both sidesof the toe portion and both sides of the heel portion of the foot platemember 12) in the present embodiment. In addition, in the presentembodiment, the ground-contacting members 17 are formed in a two-layerstructure in which a soft layer 17 a made of a relatively soft rubbermaterial and a hard layer 17 b made of a relatively hard rubber materialare vertically polymerized, and the hard layer 17 b is provided on thelowest face side thereof as a ground-contacting face portion directlymaking contact with the floor during the landing of the leg 3.

The foot mechanism 6 is provided with a landing shock absorbing device18 associated with the present invention in addition to the aboveconfiguration. The landing shock absorbing device 18 is provided with abag-like member 19 attached to the bottom face of the foot plate member12, and a flow passage 20 for flowing the air (the air in theatmosphere) as compressible fluid into and out of the interior portionof the bag-like member 19.

The bag-like member 19 is provided substantially in the center portionof the bottom face of the foot plate member 12 in such a manner that theground-contacting members 17 are presented around a periphery thereof.This bag-like member 19 is deformably structured of an elastic materialsuch as rubber or the like, so that an upwardly opened cylindricalcontainer shape is presented as shown in a solid line in FIG. 2 in anatural state that an elastic deformation is not generated by externalforces. The bag-like member 19 is designed with all the opened endportion thereof being firmly fixed on the bottom face of the foot platemember 12 and being shut and covered with the foot plate member 12.Additionally, in a natural state that the bag-like member 19 ispresented in the cylindrical container shape, the bottom face of thebag-like member 19 is provided to protrude lower than theground-contacting members 17. In other words, a height of the bag-likemember 19 (a distance from the lower face of foot plate member 12 to thebottom face of the bag-like member 19) is adapted to be taller than athickness of the ground-contacting members 17. Accordingly, in a statethat the foot plate member 12 is brought into contact with the groundthrough the ground-contacting member 17 (the landed state of the leg 3),the bag-like member 19 is compressed in a height direction of thebag-like member 19 by a floor reaction force, as shown in a phantom linein FIG. 2, or as shown about the leg 3 in the landed state in FIG. 1(the leg 3 on a forward side of the robot 1 in FIG. 1).

Further, in the present embodiment, the natural state that the bag-likemember 19 is presented in the cylindrical container shape is an inflatedstate of the bag-like member 19. The bag-like member 19 is constructedof the elastic material, resulting in having a shape restoring forceinto a shape in the natural state (the cylindrical container shape) whencompressed.

The flow passage 20 constitutes inflow/outflow means in the presentinvention, and is a flow-passing hole drilled in the foot plate member12 to have communication between the interior portion of the bag-likemember 19 and the interior portion of the tube member 13 in the presentembodiment. In this situation, as described above, the interior portionof the tube member 13 is opened to the atmospheric side, so that theflow passage 20 allows the interior portion of the bag-like member 19 tocommunicate with the atmospheric side. Therefore, the air in theatmosphere is adapted to freely come into and go out of the interiorportion of the bag-like member 19 through the flow passage 20, and inthe inflated state (the natural state) of the bag-like member 19, thebag-like member 19 is filled with the air, so that its interior pressurewill be equal to atmospheric pressure. In addition, the flow passage 20is adapted to be a throttled passage, so that fluid resistance will begenerated when the air flows into and flows out of the interior portionof the bag-like member 19.

Subsequently, in the present embodiment, a basic motion control of theleg 3 for moving the robot 1 is described. Further, this motion controlis described in details in Japanese Patent Laid-Open Publication No.10-277969, etc. by the present applicant, and hence, only a summary isdescribed herein.

The controller 10 equipped on the upper body 2 of the robot 1 executesprocessing shown in a flowchart of FIG. 4 by a predetermined controlcycle. In other words, the controller 10 first judges whether or notswitching timing is presented for a gait (a walking pattern of the leg3) of the robot 1 (STEP 1). Here, the switching timing of the gait isswitching timing of a supporting leg, and timing when the leg 3 on thefree leg side lands on the floor (when the bag-like member 19 of thefoot mechanism 6 of the leg 3 makes contact with the ground in thepresent embodiment) for example. The judgment for this timing is madebased on output of the six-axis force sensor 15 or the like for example.

When the switching timing for the gait is presented in STEP 1, afterinitializing control processing time t to “0” (STEP 2), the controller10 updates a gait parameter (STEP 3) based on a motion command of therobot 1 externally given and a predetermined movement plan of the robot1 (a plan prescribed what timing is taken and how the robot 1 is moved,etc.). Here, the gait parameter is a parameter for defining a desiredgait for one walking step of the robot 1 and for example, it is aparameter for movement modes of walking, running, and the like, lengthof a step during the robot 1 is moving, a moving speed (walking cycle),or the like. In addition, the desired gait of the robot 1 is constructedof a desired position and a trajectory of a posture of the upper body 2,a desired position and a trajectory of a posture of the foot mechanism 6of each leg 3, a desired total floor reaction force (a desired value fora resultant force of a floor reaction force each acting on both the legs3, 3), a trajectory of a desired ZMP (a desired position of an actingpoint for the total floor reaction force), and the like. Further, thedesired ZMP is more specifically a desired position of an acting pointfor a total floor reaction force to dynamically counterpoise with aresultant force of an inertia force and gravity acting on the robot 1depending on a desired motion pattern of the robot 1 defined accordingto the desired position and the trajectory of the posture of the upperbody 2 as well as the desired position and the trajectory of the postureof the foot mechanism 6 of each leg 3 (a total floor reaction force onthe same line of action with the resultant force), and a desiredposition for a point on the floor in such a way that moments (a momentabout an axis of a horizontal direction) except a moment about an axisof a vertical direction for the total floor reaction force become “0”(Zero Moment Point).

After setting a new gait parameter in STEP 3 as described above or whenit is not the switching timing of the gait in the above-mentioned STEP1, the controller 10 executes processing of STEP 4 and determines aninstantaneous desired gait as a desired gait in a current control cyclebased on a gait parameter currently set. That is to say, among thedesired gaits for one walking step of the robot 1 defined by the gaitparameters currently set, the desired gaits (the desired position andthe posture of the upper body 2 in a current time t, the desiredposition and the posture of each foot mechanism 6, the desired totalfloor reaction force, and the desired ZMP) in the current control cycle(current time t) are determined as the instantaneous desired gaits.

Subsequently, the controller 10 executes control processing for acomposite-compliance operation in STEP 5, and corrects the desiredposition and the posture of each foot mechanism 6 in the instantaneousdesired gaits determined in STEP 4. In this processing for thecomposite-compliance operation, a moment component of the total floorreaction force (hereinafter referred to as a compensating total floorreaction force's moment) to be generated around the desired ZMP (anacting point of the desired total floor reaction force) to restore theupper body 2 into the desired posture depending on a deviation betweenthe desired posture of the upper body 2 (the desired inclination angle)and an actual inclination angle of the upper body 2 detected accordingto an output such as a gyro sensor, an acceleration sensor or the likewhich is not shown is determined. At this point, the compensating totalfloor reaction force's moment to be determined is a moment about an axisof a horizontal direction, and consists of a moment component about anaxis of a forward/backward direction of the robot 1 and a momentcomponent about an axis of a right/left direction. The controller 10then corrects the desired position and the posture of each footmechanism 6 such that a resultant force of the actual floor reactionforces (the actual total floor reaction force) for each leg 3 detectedby the six-axis force sensor 15 of each leg 3 follows a resultant forcebetween the above compensating total floor reaction force's moment andthe desired total floor reaction force within a range that a groundcontacting property of the foot mechanism 6 in a ground-contacting statecan be secured. In this case, in the aforementioned desired ZMP as theacting point of the desired floor reaction force, the moment componentabout the axis of the horizontal direction (the forward/backwarddirection and the right/left direction) for the desired total floorreaction force is n. Accordingly, the corrections of the desiredposition and the posture of each foot mechanism 6 are performed to allowthe moment component about the axis of the horizontal direction for anactual total floor reaction force to follow the compensating total floorreaction force's moment. Further, in such corrections of the desiredposition and the posture of each foot mechanism 6, the desired positionand the posture of each foot mechanism 6 is corrected so as tocompensate influences of elastic deformations of the elastic member 16and the ground-contacting members 17 during the ground-contact of eachfoot mechanism 6.

Subsequently, the controller 10 determines desired displacement amountsof respective joints 7 through 9 of the two legs 3, 3 (morespecifically, desired rotational angles about each axis of respectivejoints 7 through 9) (STEP 6) by kinematics arithmetic processing basedon geometric models of the robot 1 (rigid link models) according to thedesired position and the posture of the upper body 2 of theinstantaneous desired gaits determined in the aforementioned STEP 4 andthe desired position and the posture of each foot mechanism 6 correctedin STEP 5. The controller 10 then controls torque of an electric motor(not shown) driving the respective joints 7 through 9 so as to makeactual displacement amounts of the respective joints 7 through 9 followthe determined desired displacement amount (STEP 7). Further, in thissituation, the actual displacement amounts of the respective joints 7through 9 (actual rotational angles about each axis of respective joints7 through 9) are detected by rotary encoders or the like equipped in therespective joints 7 through 9. Moreover, the controller 10 increases acontrol processing time t by a predetermined time At (time equivalent toa period of a control cycle) (STEP 8) to complete the processing of FIG.4.

According to the control processing of the controller 10 as has beendescribed, the robot 1 will move in such a way as to follow the desiredgaits while autonomously securing stability of its posture.

Subsequently, an operation of a device according to the presentembodiment, particularly an operation and an advantage of the landingshock absorbing device 18 is described. During the movement of the robot1 by the aforementioned control processing of the controller 10, firstthe bag-like member 19 makes contact with the ground when the leg 3 onthe free leg side is landing. The bag-like member 19 is compressed by afloor reaction force acting on the bag-like member 19 with a progress ofthe landing motion of the leg 3 (a movement of the leg 3 to allow thefoot plate member 12 of the foot mechanism 6 to make contact with theground through the ground-contacting members 17).

At this moment, as the bag-like member 19 is compressed, the air in thebag-like member 19 is compressed and pressurized to be flowed outthrough the flow passage 20. At this time, outflow resistance of the airis generated in the flow passage 20. Accordingly, motion energy of theleg 3 is damped. Additionally, in this situation, some of the motionenergy of the leg 3 is converted into and absorbed by elastic energy ofthe air according to spring property of the air as compressible fluid.Furthermore, the elastic energy is dispersed by the outflow resistanceof the air from the bag-like member 19. Accordingly, while avoidinginstantaneous rapid changes of the floor reaction force acting on theleg 3 through the bag-like member 19, an impact load in the landingmotion of the leg 3 (hereinafter may be referred to as a landing shock)is reduced. In this situation, the bag-like member 19 is deformable andis deformed along a shape of the floor A to be compressed, so that thelanding shock may be reduced without suffering from so much influence bythe shape of the floor A and the posture of the foot mechanism 6 justbefore landing, and the bag-like member 19 is also less prone to damageand the like.

Additionally, when the leg 3 is lifted and the floor reaction force doesnot act on the bag-like member 19, the air in the atmosphere is flowedinto the bag-like member 19 through the flow passage 20 by a restoringforce into the natural state (inflated state) of the bag-like member 19,while the bag-like member 19 is inflating. In this situation, in thepresent embodiment, the restoring force of the bag-like member 19 is setin such a manner that the bag-like member 19 is restored into thenatural state from a compressed state in a period that the leg 3equipped with the bag-like member 19 becomes the free leg. Consequently,when the landing motion of the leg 3 is performed again, the bag-likemember 19 is restored into the natural state. Accordingly, when thelanding motion of the leg 3 is performed again, the landing shock mayproperly be reduced.

On a function associated with a reduction of the landing shock, thelanding shock absorbing device 18 of the present embodiment for reducingthe landing shock in this manner is analogous to a mechanism that what aspring K1 and a damper D1 are connected in series and a spring K2 areconnected in parallel as shown in FIG. 5. The spring K1 is thecompressing spring property of the air in the bag-like member 19 herein,so that its spring constant is proportional to a pressured area at thetime that the bag-like member 19 is compressed and inverselyproportional to a height of the bag-like member 19. In addition, thedamper D1 is the outflow resistance when the air in the bag-like member19 is flowed out through the flow passage 20 which is a throttledpassage during the compression of the bag-like member 19, andconsequently, its damping effect (an attenuating property of the motionenergy) increases as an area of an aperture of the flow passage 20decreases. Additionally, the spring K2 is the restoring force into theinflated state (natural state) of the bag-like member 19, and its springconstant depends on material properties, thickness, and the like of thebag-like member 19.

In this case, in order to smoothly absorb and dissipate the motionenergy of the leg 3 in the landing motion of the leg 3 by theaforementioned operation of the landing shock absorbing device 18 of thepresent embodiment, basically, the spring constant of the spring K1 (aspring constant in the natural state of the bag-like member 19) ispreferably adapted to sufficiently be larger than the spring constant ofthe spring K2. In other words, basically, the bag-like member 19preferably has the area of its bottom portion arranged to be relativelylarger, and the restoring force from the compressed state of thebag-like member 19 to the natural state (inflated state) of the same ispreferably arranged to be relatively lower.

However, when the spring constant of the spring K1 is increased toomuch, a peak load (a peak load value of the floor reaction force) actingon the leg 3 through the bag-like member 19 tends to become large duringthe landing motion of the leg 3. On the contrary, when the springconstant of the spring K1 is decreased too much, the attenuatingproperty of vibrations of the floor reaction force immediately after thelanding of the leg 3 decreases. In addition, when the spring constant ofthe spring K2 is too small, the restoring force of the bag-like member19 becomes weak. Particularly, when the moving speed of the robot 1 isrelatively fast, after the lifting motion of the leg 3 until the leg 3is landed next time, the bag-like member 19 may not sufficiently berestored into the natural state or a state close thereto.

Accordingly, in the landing shock absorbing device 18 of the presentembodiment, a size of the bag-like member 19, the restoring force of thebag-like member 19 and the like are set in consideration of thesepoints. Consequently, the landing shock absorbing device 18 can properlyreduce the impact during the landing motion of the leg 3.

Additionally, the landing shock absorbing device 18 of the presentembodiment may bring the following effects. In other words, fluid thatflows into and out of the bag-like member 19 is the air of thecompressible fluid, and hence the landing shock absorbing device 18 maybe configured to be lightweight. Furthermore, during the landing motionof the leg 3, the pressure within the bag-like member 19 is increasedwith certain degree of a time constant and not increasedinstantaneously, so that the rapid change in the floor reaction forcemay be avoided. In addition, the air flowed out of the bag-like member19 when the bag-like member 19 is compressed is released into theatmosphere and new air flows into the bag-like member 19 from theatmosphere when the bag-like member 19 is inflated, and resultingly,heat generated with outflow resistance of the air from the bag-likemember 19 will not be stored in the bag-like member 19. In other words,the landing shock absorbing device 18 has a good heat dissipationproperty, so that a heat managing instrument such as an radiator doesnot need to be provided.

Additionally, the spring constant of the air in the bag-like member 19functioning as a spring during the landing motion of the leg 3 becomessmall with the compression immediately after the bag-like member 19touches the ground, and hence an effect of control of the aforementionedcomposite-compliance operation may be enhanced. That is to say, in thecontrol of the composite-compliance operation of the robot 1, asdescribed above, the position and the posture of each foot mechanism 6is corrected so as to allow the moment component about the axis of thehorizontal direction for the actual total floor reaction force(hereinafter referred to as an actual total floor reaction force'smoment) to follow the compensating total floor reaction force's moment(also including an occasion that the compensating total floor reactionforce's moment is “0”) as a desired value of the moment component. Thecomposite-compliance operation control like this is for making thelanding position and the posture of the foot mechanism 6 adjust to thefloor A to secure the stability of the posture of the robot 1, even whenthe floor A has an inclination. In this situation, in order to enhance afollowing-property of the actual total floor reaction force moment tothe compensating total floor reaction force's moment, it is preferablethat a compliance gain in the composite-compliance operation control ora change amount of the desired landing position and the posture of thefoot mechanism 6 to a change of the deviation between the actual totalfloor reaction force's moment and the compensating total floor reactionforce's moment (a change amount of the rotational angle of the anklejoint 9) is increased. However, when the above compliance gain is takento be big, in general, a loop gain of the composite compliance operationcontrol (generally, this is proportional to the product of the abovecompliance gain and the total spring constant of the spring mechanismwhich the foot mechanism 6 has (the ground-contacting members 17, theelastic member 16, and the landing shock absorbing device 18)) becomesbig, and resultantly, a control system tends to be unstable.

However, the spring constant of the air in the bag-like member 19functioning as the spring K1 of the landing shock absorbing device 18 ofthe present embodiment becomes small with the compression immediatelyafter the bag-like member 19 touches the ground, and hence the aboveloop gain becomes small. As a result, even when the compliance gain isincreased, the stability of the composite compliance operation controlmay be secured. Consequently, the following-property of the actual totalfloor reaction force's moment to the compensating total floor reactionforce's moment may be improved and furthermore, the securement of thestability of the posture of the robot 1 may be improved.

Subsequently, referring to FIG. 6, a second embodiment of the presentinvention is described. FIG. 6 is a cross sectional view showing a sideface of the foot mechanism equipped with a landing shock absorbingdevice. Further, the present embodiment differs from the firstembodiment only in a shape of a bag-like member, so that the referencenumerals identical to those of the first embodiment are used.Descriptions about component portions identical to those of the firstembodiment are omitted.

In the first embodiment, the bag-like member 19 formed in a cylindricalshape has been shown. However, the bag-like member 19 formed in acylindrical shape tends to become deformed into a barrel shape in astate that the air in the bag-like member 19 is not so much pressuredimmediately after the bag-like member 19 makes contact with the groundduring the landing motion of the foot mechanism 6. In the landing shockabsorbing device 18 of the present embodiment, as shown in FIG. 6, abag-like member 19 formed to be in the barrel shape in the natural stateis attached on the bottom face of a foot plate member 12. Configurationsother than this (including the control processing of the controller 10)are totally identical to those of the first embodiment.

In the landing shock absorbing device 18 of the present embodiment likethis, the air in the bag-like member 19 is applied with pressureimmediately after the bag-like member 19 makes contact with the ground,and hence a quick responding property of a shock absorbing operation forthe landing shock caused by the landing shock absorbing device 18 isenhanced. Acting effects other than this are the same as those of thefirst embodiment.

Further, in the first and the second embodiments described above, theflow passage 20 of the air flowing into and flowing out of the bag-likemember 19 is configured by a flow-passing hole drilled in the foot platemember 12, but a hose tube may also be used to constitute thereof.

Additionally, in the first and the second embodiments, the bag-likemember 19 is constructed of the elastic material, thereby giving theshape restoring force to the bag-like member 19. However, for example,the bag-like member 19 may be constructed of a raw material withouthaving the restoring force and the bag-like member 19 may also beenergized into a predetermined inflated state by a different spring suchas a coil spring.

Additionally, in the first and the second embodiments, the bag-likemember 19 is shown in an upwardly opened type, but may also be a sealedtype. In this situation, a flow-passing hole is drilled in the bag-likemember, and an inflow and an outflow of the air with respect to theinside of the bag-like member may be executed through the flow-passinghole. Alternatively, a raw material having a plurality of fine holessuch as a cloth, a net, a porous material, or the like may alsoconstitute the bag-like member.

Subsequently, referring to FIG. 7(a) and FIG. 7(b), a third embodimentof the present invention is described. FIG. 7(a) and FIG. 7(b) are crosssectional views showing a configuration of infow/outflow means of alanding shock absorbing device of the present embodiment. Further, thepresent embodiment differs from the second embodiment only in theconfiguration of the inflow/outflow means, so that regarding componentportions or function portions identical to those of the secondembodiment, the reference numerals identical to those of the secondembodiment are used, thereby omitting descriptions thereof.

As shown in FIG. 7, in the landing shock absorbing device in the presentembodiment, inflow/outflow means 23 is equipped with a hollow valvechamber element 24 upwardly extended from the foot plate member 12 ofeach foot mechanism 6 and a discoidal valve element 25 provided in aninterior of this valve chamber element 24. The interior of the valvechamber element 24 is communicated with the inside of the bag-likemember 19 through a flow-passing hole 24 a drilled in a lower endportion of the valve chamber element as well as with the atmosphericside through a flow-passing hole 24 b drilled in an upper end portion ofthe valve chamber element 24.

The valve element 25 is provided with the flow-passing hole 25 a drilledin the center portion thereof, and a notch portion 25 b on one endportion (a left end portion in the figure. Additionally, the valveelement 25 is adapted to be pivotable in a direction that the endportion with the notch portion 25 b moves up and down, having a spindle26 provided on the other end portion (a right end portion in the figure)as a supporting point. In this case, the valve element 25 is pivotablebetween a state that its top face portion abuts the upper end portion ofthe valve chamber element 24 as shown in FIG. 7(a) and a state that alower end portion of the valve element 25 (an end portion having thenotch portion 25 b) abuts the lower end portion of the valve chamberelement 24 as shown in FIG. 7(b), and in the state of FIG. 7(a), thenotch portion 25 b of the valve element 25 is closed and covered by theupper end portion of the valve chamber element 24 so as to allow theflow-passing hole 24 a on the side of the bag-like member 19 and theflow-passing hole 24 b on the atmospheric side to communicate with eachother only through the flow-passing hole 25 a. In the state of FIG.7(b), both the flow-passing holes 24 a and 24 b are then adapted to beput in communication with each other through both of the flow-passinghole 25 a and the notch portion 25 b of the valve element 25. Inaddition, during the compression of the bag-like member 19 associatedwith the landing motion of the foot mechanism 6, the valve element 25 ispivoted into the state in FIG. 7(a) by rise in pressure in the bag-likemember 19, and during the inflation of the bag-like member 19 associatedwith lifting of the foot mechanism 6, the valve element 25 is pivotedinto the state in FIG. 7(b) by a negative pressure and a gravitygenerated in the bag-like member 19. Configurations except what has beendescribed (including the control processing of the controller 10) areidentical to those of the second embodiment.

In the landing shock absorbing device of the present embodiment equippedwith the inflow/outflow means 23 in the configuration like this, the airflowing into the bag-like member 19 during the inflation of the bag-likemember 19 passes through both of the flow-passing hole 25 a and thenotch portion 25 b of the valve element 25 as shown in arrows in FIG.7(b), so that its inflow resistance is relatively low. As a result, thebag-like member 19 may quickly be returned to the natural state (theinflated state).

In contrast, the air flowed out of the bag-like member 19 during thecompression of the bag-like member 19 passes only through theflow-passing hole 25 a of the valve element 25 as shown in an arrow inFIG. 7(a), so that its outflow resistance will be relatively great. As aresult, a damping effect of the landing shock absorbing device accordingto its outflow resistance may be enhanced. Acting effects other thanthis are similar to those of the second embodiment.

Subsequently, referring to FIG. 8, a fourth embodiment of the presentinvention is described. FIG. 8 is a view in schematic form showingsubstantial portions of the foot mechanism equipped with a landing shockabsorbing device of the present embodiment. Further, in the presentembodiment, the foot mechanism is identical to that of the secondembodiment except a configuration relating to the landing shockabsorbing device, and only a configuration of the substantial portionsof the foot mechanism is described in FIG. 8. Additionally, in adescription of the present embodiment, regarding component portions orfunction portions identical to those of the second embodiment, thereference numerals identical to those of the second embodiment are used,thereby omitting descriptions thereof.

The present embodiment is configured by using inflow/outflow means suchas a check valve or the like having a function equal to that of theinflow/outflow means 23 of the landing shock absorbing device of thethird embodiment. Namely, referring to FIG. 8, in the presentembodiment, inflow/outflow means 26 of the landing shock absorbingdevice 18 is equipped with a pair of fluid conduits 27, 28 communicatedwith the inside of the bag-like member 19 and lead out from the side ofthe bag-like member 19. These fluid conduits 27, 28 are opened to theatmospheric side through a joined conduit 29 joined to a far end portionthereof (an end portion on the opposite side of the bag-like member 19).A throttle portion 30 is provided in the fluid conduit 27 and a checkvalve 31 is provided in the fluid conduit 28. In this situation, thecheck valve 31 is provided to shut off the air from flowing out of thebag-like member 19 through the fluid conduit 28. Configurations otherthan such the inflow/outflow means 26 (including the control processingof the controller 10) are identical to those of the second embodiment.

In the landing shock absorbing device 18 equipped with theinflow/outflow means 26 like this, during the compression of thebag-like member 19, the air flows out into the atmosphere from theinside of the bag-like member 19 through the fluid conduit 27 having thethrottle portion 30 and the joined conduit 29, and the air will not flowinto the fluid conduit 28 by the check valve 31. Consequently, itsoutflow resistance will be relatively great. Additionally, when thebag-like member 19 is inflated, the air in the atmosphere flows from thejoined conduit 29 through both the fluid conduits 27 and 28 into thebag-like member 19. Consequently, its inflow resistance will berelatively small. As a result, an acting effect equal to that of thethird embodiment is achieved.

Further, in the present embodiment, the throttle portion 30 and thecheck valve 31 are constructed separately, but the inflow/outflow means26 of the present embodiment may also be constructed using a one-waythrottle valve in a usual structure.

Subsequently, referring to FIG. 9, a fifth embodiment of the presentinvention is described. FIG. 9 is a view in schematic form showingsubstantial portions of a foot mechanism equipped with a landing shockabsorbing device of the present embodiment. Further, in the presentembodiment, the foot mechanism is identical to that of the secondembodiment excluding a configuration relating to the landing shockabsorbing device, and only a configuration of the substantial portionsof the foot mechanism is described in FIG. 9. Additionally, in adescription of the present embodiment, regarding component portions orfunction portions identical to those of the second embodiment, thereference numerals identical to those of the second embodiment are used,thereby omitting descriptions thereof.

The aforementioned first to fourth embodiments are shown with acompletely or a partially shared flow passage for executinginflow/outflow of the air to the bag-like member 19, respectively, butthe present embodiment is designed to perform the inflow of the air intothe bag-like member 19 and the outflow of the air from the bag-likemember 19 in individual flow passages. In other words, inflow/outflowmeans 32 of the landing shock absorbing device 18 in the presentembodiment is equipped with a pair of fluid conduits 33, 34 communicatedwith the inside of the bag-like member 19 and lead out from the side ofthe bag-like member 19, with far end portions of these fluid conduits33, 34 (end portions on the opposite side to the bag-like member 19)being opened to the atmospheric side. The fluid conduit 33 is providedwith a check valve 35 for blocking the inflow of the air into thebag-like member 19 and a throttle portion 36, and the fluid conduit 34is provided with a check valve 37 for blocking the outflow of the airfrom the bag-like member 19 and a throttle portion 38. In thissituation, an area of an aperture of the throttle portion 36 of thefluid conduit 33 is arranged to be smaller than an area of an apertureof the throttle portion 38 of the fluid conduit 34. Further, the area ofthe aperture of the throttle portion 38 of the fluid conduit 34 may beequal to the area of the aperture of the other portion of the fluidconduit 34. Configurations other than the configuration described above(including the control processing of the controller 10) are identical tothose of the second embodiment.

In the landing shock absorbing device 18 equipped with theinflow/outflow means 32 like this, when the bag-like member 19 iscompressed, the air in the bag-like member 19 is flowed out to theatmospheric side only through the fluid conduit 33, and the outflowresistance at this time is defined by the throttle portion 36.Additionally, when the bag-like member 19 is inflated, the air in theatmospheric side flows into the bag-like member 19 only through thefluid conduit 34, and the inflow resistance at this time is defined bythe throttle portion 38. Consequently, the inflow and outflowresistances of the air to the bag-like member 19 are individually set ina desired characteristic. Additionally, in the present embodiment, thearea of the aperture of the throttle portion 36 is smaller than the areaof the aperture of the throttle portion 38, and hence the outflowresistance of the air to the bag-like member 19 is greater than theinflow resistance. Consequently, an acting effect equal to that of thethird or fourth embodiment is achieved. Acting effects other than thisare equal to those of the second embodiment.

Further, in respects of a simplification of the configuration of theinflow/outflow means and a reduction of component counts, theaforementioned first to fourth embodiments in which the inflow andoutflow of the air into the bag-like member 19 is carried out by sharinga complete or a partial flow passage are advantageous.

Additionally, in the present embodiment, the check valve 35 of the fluidconduit 33 may be omitted, and in this case, when the bag-like member 19is inflated, the air will flow into the bag-like member 19 through boththe fluid conduits 33 and 34. However, air volume flowing into thebag-like member 19 through the fluid conduit 33 will be more than airvolume flowing into the bag-like member 19 through the fluid conduit 34.

Subsequently, referring to FIG. 10, a sixth embodiment of the presentinvention is described. FIG. 10 is a view in schematic form showingsubstantial portions of a foot mechanism equipped with a landing shockabsorbing device of the present embodiment. Further, in the presentembodiment, the foot mechanism is identical to that of the secondembodiment excluding a configuration relating to the landing shockabsorbing device, and only a configuration of the substantial portionsof the foot mechanism is described in FIG. 10. Additionally, in adescription of the present embodiment, regarding component portions orfunction portions identical to those of the second embodiment, thereference numerals identical to those of the second embodiment are used,thereby omitting descriptions thereof.

In the landing shock absorbing device 18 of the present embodiment, asinflow/outflow means 39, a pair of fluid conduits 40, 41 communicatedwith the inside of the bag-like member 19 and lead out from the side ofthe bag-like member 19 are provided, with far end portions of thesefluid conduits 40, 41 (an end portion on the opposite side to thebag-like member 19) being opened to the atmospheric side. The fluidconduit 40 is provided with a variable throttle 42 (a solenoidproportional valve) which can electromagnetically control an area of anaperture by the controller 10, and the fluid conduit 41 is provided witha check valve 43 for blocking the air from flowing out of the bag-likemember 19 through the fluid conduit 41. In this situation, in thepresent embodiment, as a moving speed of the robot 1 increases, thecontroller 10 controls the variable throttle 42 to reduce the area ofthe aperture of the variable throttle 42. Configurations other than this(including the control processing of the controller 10) are identical tothose of the second embodiment.

In the landing shock absorbing device 18 of the present embodiment likethis, during the compression of the bag-like member 19, the air in thebag-like member 19 flows out to the atmospheric side through the fluidconduit 40 having the variable throttle 42. Additionally, during theinflation of the bag-like member 19, the air in the atmosphere flowsinto the bag-like member 19 through both the fluid conduits 40, 41(however, a large portion of the air flows into the bag-like member 19through the fluid conduits 41). Consequently, regarding a magnituderelation between the outflow resistance and the inflow resistance of theair to the bag-like member 19, it is similar to that of theaforementioned third to fifth embodiments.

On the other hand, in the present embodiment, as the moving speed of therobot 1 increases, the area of the aperture of the variable throttle 42is reduced to increase the outflow resistance of the air from thebag-like member 19, resulting in enhancing the damping effect.Accordingly, as the moving speed of the robot 1 increases, a floorreaction force acting on the leg 3 may quickly be put into a steadystate during the landing motion of each leg 3. Regarding acting effectsother than this, these are similar to those of the second embodiment.

Subsequently, referring to FIG. 11, a seventh embodiment of the presentinvention is described. FIG. 11 is a view in schematic form showingsubstantial portions of a foot mechanism equipped with a landing shockabsorbing device of the present embodiment. Further, in the presentembodiment, the foot mechanism is identical to that of the secondembodiment excluding a configuration relating to the landing shockabsorbing device, and only a configuration of the substantial portionsof the foot mechanism is described in FIG. 11. Additionally, in adescription of the present embodiment, regarding component portions orfunction portions identical to those of the second embodiment, thereference numerals identical to those of the second embodiment are used,thereby omitting descriptions.

In the landing shock absorbing device 18 of the present embodiment, asinflow/outflow means 44, three fluid conduits 45, 46, and 47communicated with the inside of the bag-like member 19 and lead out fromthe side of the bag-like member 19 are provided, with far end portionsof these fluid conduits 45 to 47 (an end portion on the opposite side tothe bag-like member 19) being opened to the atmospheric side. The fluidconduit 45 is provided with a throttle portion 48, and the fluid conduit46 is provided with a check valve 49 for blocking the air from flowingout of the bag-like member 19 through the fluid conduit 46. Furthermore,the fluid conduit 47 is provided with a relief valve 50 which canelectromagnetically control a setting pressure by the controller 10. Inthis situation, in the present embodiment, as a moving speed of therobot 1 increases, the controller 10 controls the relief valve 50 toincrease the setting pressure of the relief valve 50. Configurationsother than this (including the control processing of the controller 10)are identical to those of the second embodiment.

In the landing shock absorbing device 18 of the present embodiment likethis, during the compression of the bag-like member 19, the air in thebag-like member 19 flows out to the atmospheric side through the fluidconduit 45 having the throttle portion 48. Additionally, during theinflation of the bag-like member 19, the air in the atmosphere flowsinto the bag-like member 19 through both the fluid conduits 45, 46(however, a large portion of the air flows into the bag-like member 19through the fluid conduits 46). Consequently, regarding a magnituderelation between the outflow resistance and the inflow resistance of theair to the bag-like member 19, it is similar to that of theaforementioned third to sixth embodiments.

In contrast, in the present embodiment, during the compression of thebag-like member 19, when a pressure in the bag-like member 19 exceedsthe setting pressure of the relief valve 50, the relief valve 50 isopened to block a further rise in the pressure in the bag-like member19. This may prevent the pressure in the bag-like member 19 from risingexcessively. In this case, generally, as the moving speed of the robot 1increases, motion energy of the leg 3 increases, and hence in absorbingthe motion energy, as the moving speed of the robot 1 increases, thepressure in the bag-like member 19 is preferably brought up to a higherpressure. Accordingly, in the present embodiment, as the moving speed ofthe robot 1 increases, the setting pressure of the relief valve 50 isadapted to be increased. Consequently, a reducing effect of the landingshock by the landing shock absorbing device 18 may properly be ensuredwithout depending on the moving speed of the robot 1.

Subsequently, referring to FIG. 12 and FIG. 13, an eighth embodiment isdescribed. FIG. 12 is a view in schematic form showing substantialportions of a foot mechanism equipped with a landing shock absorbingdevice of the present embodiment, and FIG. 13 is a diagram fordescribing an operation of the landing shock absorbing device of thepresent embodiment. Further, in the present embodiment, the footmechanism is identical to that of the second embodiment excluding aconfiguration relating to the landing shock absorbing device, and only aconfiguration of the substantial portions of the foot mechanism isdescribed in FIG. 12. Additionally, in a description of the presentembodiment, regarding component portions or function portions identicalto those of the second embodiment, the reference numerals identical tothose of the second embodiment are used, thereby omitting descriptionsthereof.

Referring to FIG. 12, in the landing shock absorbing device 18 of thepresent embodiment, as inflow/outflow means 51, a pair of fluid conduits52, 53 communicated with the inside of the bag-like member 19 and leadout form the side of the bag-like member 19 are provided, and far endportions of these fluid conduits 52, 53 (an end portion on the oppositeside to the bag-like member 19) are connected to an air pressure source56 comprising an accumulator 54 and a pressure pump 55. The air pressuresource 56 is a resource of the air in a predetermined pressure higherthan the atmospheric pressure. In the fluid conduit 52, a throttleportion 57 and a check valve 58 for blocking the air from flowing intothe bag-like member 19 through the fluid conduit 52 are provided, and inthe fluid conduit 53, a throttle portion 59, a check valve 60 forblocking the air from flowing into the bag-like member 19 through thefluid conduit 53, and a solenoid valve 61 which can be controlled by thecontroller 10 are provided. In this case, an area of an aperture of thethrottle portion 57 is designed to be smaller than the area of theaperture of the throttle portion 59.

Additionally, in the present embodiment, the bag-like member 19, in ainflated state as its natural state (in a state shown in FIG. 12), isadapted to be maintained in a shape in the natural state, so that almostno elastic force (shape restoring force) will be generated, even whenits internal pressure becomes higher than the atmospheric pressure. Thatis to say, regarding a capacity of the bag-like member 19, its capacityin the natural state is adapted to substantially be the upper limitcapacity. The bag-like member 19 in this fashion is constructed of, forexample, an elastic material mixed with an unstretchable material suchas a hard-to-stretch elastic material and ground fabric. Moreover, inthe present embodiment, for example, in the lifting state of the leg 3,the controller 10 controls the solenoid valve 61 to open, and in thelanding state of the leg 3, the controller 10 controls the solenoidvalve 61 to close. Configurations other than the configuration describedabove (including the control processing of the controller 10) areidentical to those of the second embodiment.

In the landing shock absorbing device 18 of the present embodiment likethis, the solenoid valve 61 is opened in the lifting state of the leg 3.Accordingly, in the lifting state of the leg 3, the air pressured higherthan the atmospheric pressure flows from the aforementioned air pressuresource 56 through the fluid conduit 53 into the bag-like member 19, andhence the bag-like member 19 is inflated into the natural state (thestate shown in FIG. 12). In this situation, an area of an aperture ofthe throttle portion 59 of the fluid conduit 53 is relatively wide, sothat the inflow resistance of the air into the bag-like member 19 isrelatively small, and the bag-like member 19 quickly inflates into thenatural state (inflated state). Additionally, in this situation,regarding the bag-like member 19, the shape restoring force is notgenerated in the natural state in the present embodiment, and hence inthe inflated state of the bag-like member 19, the air in the bag-likemember 29 will have a preload according to a difference between thepressure in the bag-like member 19 and the atmospheric pressure.

Additionally, during the landing motion of the leg 3, after the bag-likemember 19 touches the ground associated with the landing motion, thebag-like member 19 is compressed and pressurized with its internal air,so that the air flows out of the bag-like member 19 through the fluidconduit 52. At this time, the outflow resistance of the air is generatedby the throttle portion 57 of the fluid conduit 52. According to this,basically, the landing shock may be reduced as in the above-mentionedfirst to seventh embodiments. In this situation, an area of an apertureof the throttle portion 57 of the fluid conduit 52 is relatively smalland the pressure of the air flowed out of the bag-like member 19 ishigh, and consequently, the outflow resistance of the air during thecompression of the bag-like member 19 increases, so that the dampingeffect of the landing shock absorbing device 18 of the presentembodiment may be enhanced.

Furthermore, in the present embodiment, particularly, in the inflatedstate of the bag-like member 19, preload is given to the air in theinterior thereof. Consequently, as shown in FIG. 13, reaction forcegenerated with the compression of the bag-like member 19 rapidlyincreases immediately after the bag-like member 19 starts to becompressed, and after that, the reaction force will linearly increasewith an increase in a compression amount of the bag-like member 19 (acompression amount of the bag-like member 19 in a vertical direction).Consequently, immediately after the bag-like member 19 touches theground with the landing motion of the leg 3, momentum of the footmechanism 6 of the leg 3 may rapidly be decreased (an impulse in adirection that the momentum of the foot mechanism 6 is decreasedimmediately after the bag-like member 19 touches the ground may beincreased), and then a peak value for an impact load (floor reactionforce) acting on the leg 3 during the landing motion of the leg 3 may bedecreased. In other words, a reducing effect of the landing shock may beenhanced.

Furthermore, in the present embodiment, in the landing state of the leg3, the solenoid valve 61 is closed, and consequently, the air can notflow into the bag-like member 19, so that the bag-like member 19 ismaintained in the compressed state. Therefore, the floor reaction forcemay be acted intensively on a desired area of the foot mechanism 6 by aposture control in the landing state of the foot mechanism 6 without thefloor reaction force acting on a spot of the bag-like member 19. Forexample, when robot 1 is about to forwardly topple over, the floorreaction force can be concentrated on the front end side of the footmechanism 6. As a result, the posture of the robot 1 may easily bestabilized. Further, in an additional description about this, if thesolenoid valve 61 is kept opened in the landing state of the leg 3,high-pressure air always attempts to flow into the bag-like member 19from the air pressure source 56 (the bag-like member 19 attempts toinflate), and hence the floor reaction force will always act on the spotof the bag-like member 19. Accordingly, the floor reaction force can notbe concentrated on the desired area of the foot mechanism 6, so thatstabilization of the posture of the robot 1 by a posture control in thelanding state of the foot mechanism 6 tends to be limited. With respectto this, in the landing shock absorbing device 18 of the presentembodiment, the limitation on stabilization of the posture of the robot1 may be improved, as described above.

Further, in the above eighth embodiment, the bag-like member 19 isconstructed of the elastic material, but may also be constructed of aflexible material that does not have elasticity. In the eighthembodiment, also in this manner, the high-pressure air is flowed intothe bag-like member 19, so that the bag-like member 19 may be inflated.Additionally, regarding an open/close control of the solenoid valve 61,in a period immediately after the leg 3 is moved from the landing stateinto the lifting state, the bag-like member 19 may also be maintained inthe compressed state in a manner that the solenoid valve 61 is heldclosed. This allows the lifting motion of the leg 3 to be carried outsmoothly.

Additionally, in the aforementioned eighth embodiment, the use of ahard-to-stretch material or the like allows the air in the bag-likemember 19 to have preload in such a way to prevent the bag-like member19 from inflating more than the natural state. However, the air in thebag-like member 19 may also have preload by structurally preventing thebag-like member 19 from inflating more than the natural state, even whenits internal pressure is arranged to be higher than the atmosphere. Suchexamples of preload giving mechanisms as a ninth embodiment and a tenthembodiment are shown in FIG. 14 and FIG. 15, respectively. Further, inFIG. 14 and FIG. 15, the same reference numerals are given to componentportions identical to those of the eighth embodiment.

In the ninth embodiment shown in FIG. 14, a plate member 61 is fixed ona bottom face portion in a bag-like member 19, and this plate member 61is connected through a flexible wire 62 to a foot plate member 12 in theinterior portion of the bag-like member 19. The other configurations areidentical to those of the eighth embodiment. In this ninth embodiment, astate that the wire 62 is stretched is an inflated state of the bag-likemember 19, so that the bag-like member 19 will not be inflated more thanthis state. Consequently, in the inflated state of the bag-like member19, the air of its interior portion may be given with preload as in theeighth embodiment. Further, the stretched wire 62 allows a compressionof the bag-like member 19 to be executed without any problem.

In the tenth embodiment shown in FIG. 15, a plate member 63 is fixed ona bottom face portion in a bag-like member 19, and a rod member 64upwardly extended from this plate member 63 slidably passes through afoot plate member 12 in a vertical direction (a compressed direction ofthe bag-like member 19) to protrude to the upper side. A stopper plate65 is fixed on the upper end portion of the rod member 64, and thisstopper plate 65 abuts against a top face portion of the foot platemember 12 so as to control a downward movement of the rod member 64. Theother configurations are identical to those of the eighth embodiment. Inthis tenth embodiment, a state that the stopper plate 65 is abuttedagainst the top face portion of the foot plate member 12 is an inflatedstate of the bag-like member 19, so that the bag-like member 19 will notbe inflated more than this state. Consequently, in the inflated state ofthe bag-like member 19, the air of its interior portion may be givenwith preload as in the eighth embodiment. Further, the rod member 64moves upward with the stopper plate 65 upwardly leaving from the footplate member 12, so that the compression of the bag-like member 19 isexecuted without any trouble.

Subsequently, referring to FIG. 16 and FIG. 17, an eleventh embodimentis described. FIG. 16 is a view in schematic form showing substantialportions of a foot mechanism equipped with a landing shock absorbingdevice of the present embodiment, and FIG. 17 is a flowchart showingcontrol processing associated with the present embodiment. Still more,in the present embodiment, the foot mechanism is identical to that ofthe second embodiment except a configuration with respect to the landingshock absorbing device, and in FIG. 16, only the configuration of thesubstantial portions of the foot mechanism is described. Additionally,in a description of the present embodiment, regarding component portionsor function portions identical to the second embodiment, referencenumerals identical to those of the second embodiment are used, therebyomitting descriptions thereof.

As shown in FIG. 16, in a landing shock absorbing device 18 of thepresent embodiment, a pair of fluid conduits 67, 68 communicated withthe inside of a bag-like member 19 and lead out from a side of thebag-like member 19 are provided as inflow/outflow means 66, and a farend portion of the fluid conduit 67 (an end portion on the opposite sideto the bag-like member 19) is connected to an air chamber 69 filled withthe air. In addition, a far end portion of the fluid conduit 68 (an endportion on the opposite side to the bag-like member 19) is opened to theatmospheric side. These fluid conduits 67, 68 are provided with solenoidproportional valves 70, 71 with its opened/closed state being controlledby the controller 10, respectively. Moreover, in the interior portion ofthe bag-like member 19, a pressure sensor 72 for detecting pressure ofits interior portion is provided, and its output is adapted to be inputinto the controller 10. Still more, pressure of the air in the airchamber 69 is higher than the atmospheric pressure. Additionally, thebag-like member 19 is constructed of a hard-to-stretch elastic materialas in the eighth embodiment in such a way to hardly be inflated morethan the natural state, when the pressure of its interior portion ishigher than the atmospheric pressure. Additionally, in the followingdescription, the solenoid proportional valve 70 is referred to as an airchamber side solenoid proportional valve 70, and the solenoidproportional valve 71 is referred to as an atmospheric side solenoidproportional valve 71.

In this situation, in the present embodiment, the controller 10 executesprocessing shown in the flowchart of FIG. 17 for each leg 3 in parallelwith the motion control of the robot 1, and for each control cycle inparallel with the processing of STEP 5 in the flowchart of theaforementioned FIG. 4, resulting in controlling an opened/closed stateof the solenoid proportional valves 70, 71.

That is to say, depending on gait parameters currently set (movementmodes, length of step, moving speed, etc. of the robot 1), thecontroller 10 sets atmospheric air intake time Tin defining a period tomake the air in the atmosphere flow into the bag-like member 19 in alifting state of the leg 3, pressure-up time Tup defining a period thatthe air in the air chamber 69 is flowed into the bag-like member 19 inthe lifting state of the leg 3 to increase the pressure in the bag-likemember 19, and switching pressure Pc defining timing that the air in thebag-like member 19 is flowed out to the atmospheric side after thebag-like member 19 touches the ground during the landing motion of theleg 3 (STEP 11). Further, basically, the atmospheric air intake time Tinis set at a shorter time as the moving speed of the robot 1 increases,basically, the pressure-up time Tup is set at a longer time as themoving speed of the robot 1 increases, and basically, the switchingpressure Pc is set at higher pressure as the moving speed of the robot 1increases.

Furthermore, based on the gait parameters currently set, the controller10 determines a time Tsup that the leg 3 is in a supporting leg stage(time that the foot mechanism 6 is maintained in a state that the footmechanism 6 is put in contact with the ground through theground-contacting members 17 or the bag-like member 19, and hereinafterreferred to as a supporting leg time Tsup) (STEP 12).

Subsequently, the controller 10 judges whether or not current time t is0≦t<Tsup, and in other words, judges whether or not the current time tis timing in the supporting leg stage (STEP 13). At this moment, whenthe current time t is in the supporting leg stage, the controller 10further judges whether or not the detected pressure by the pressuresensor 72 has risen up to the switching pressure PC (STEP 14), and whenthe detected pressure has not risen up to the switching pressure Pc, theatmospheric side solenoid proportional valve 71 is held in a totallyclosed state and the air chamber side solenoid proportional valve 70 isheld in a half opened state (STEP 15). Additionally, in STEP 14, whenthe detected pressure has risen up to the switching pressure Pc, theatmospheric side solenoid proportional valve 71 is held in a half openedstate, and the air chamber side solenoid proportional valve 70 is heldin the totally closed state (STEP 16). Further, in this case, afterexecuting the processing of the STEP 16, as long as the current time tis in the supporting leg stage, even when the detected pressure dropslower than the switching pressure Pc, the controller 10 holds theatmospheric side solenoid proportional valve 71 in the half opened stateand the air chamber side solenoid proportional valve 70 in the totallyclosed state.

In the aforementioned STEP 13, when it is not 0≦t<Tsup, the controller10 further judges whether or not the current time t is Tsupst<Tsup+Tin,in other words, whether or not it is in a period until the atmosphericair intake time Tin has elapsed after the supporting leg stage of theleg 3 is ended (hereinafter, this period is referred to as anatmospheric air intake period) (STEP 17). At this time, when the currenttime t is in the atmospheric air intake period, the controller 10 holdsthe atmospheric side solenoid proportional valve 71 in a totally openedstate and the air chamber side solenoid proportional valve 70 in thetotally closed state (STEP 18).

Furthermore, in STEP 17, when it is not Tsupst<Tsup+Tin, the controller10 judges whether or not the current time t is Tsup+Tinst<Tsup+Tin+Tup,in other words, whether or not it is within a period after theatmospheric air intake period has elapsed until the pressure-up time Tupelapses (hereinafter, this period is referred to as a pressure-upperiod) (STEP 19). At this time, when the current time t is within thepressure-up period, the controller 10 holds the atmospheric sidesolenoid proportional valve 71 in the totally closed state, and the airchamber side solenoid proportional valve 70 in the totally opened state(STEP 20).

Additionally, in STEP 19, when the current time t is not in thepressure-up period (it is not in the supporting leg stage or theatmospheric air intake period), as in the aforementioned STEP 15, thecontroller 10 holds the atmospheric side solenoid proportional valve 71in the totally closed state and the solenoid proportional valve 70 inthe half opened state (STEP 21).

In the landing shock absorbing device 18 of the present embodimentcontrolling the opened/closed state of the solenoid proportional valves70, 71 in this fashion, from shortly before the bag-like member 19 ofthe leg 3 touches the ground, the atmospheric side solenoid proportionalvalve 71 is held in the totally closed state and the air chamber sidesolenoid proportional valve 70 is held in the half opened state.Accordingly, in moments after the bag-like member 19 touches the groundwith the landing motion of the leg 3, while the bag-like member 19 andthe air of its interior portion are compressed and pressurized, the airin the bag-like member 19 flows out to the air chamber 69 through athrottle formed by the air chamber side solenoid proportional valve 70in the half opened state. Consequently, the air in the bag-like member19 flows out with the outflow resistance and the damping effect isgenerated. Further, at this time, the pressure in the air chamber 69rises to become high pressure.

Moreover, when the compression of the bag-like member 19 proceeds andthe pressure of its interior portion exceeds the switching pressure Pc,the atmospheric side solenoid proportional valve 71 is held in the halfopened state and the air chamber side solenoid proportional valve 70 isheld in the totally closed state. Accordingly, the air in the bag-likemember 19 flows out to the atmospheric side through the throttle formedby the atmospheric side solenoid proportional valve 71 in the halfopened state. Consequently, in the same way as immediately after thebag-like member 19 makes contact with the ground, the air in thebag-like member 19 flows out with the outflow resistance, and hence thedamping effect is generated. Such a compression of the bag-like member19 and an outflow motion of the air of its interior portion during thelanding motion of the leg 3 allows the landing shock to be reduced as inthe second embodiment or the like.

On the contrary, after the elapse of the supporting leg stage of the leg3, in the atmospheric air intake period immediately after the supportingleg stage of the leg 3 has ended, the atmospheric side solenoidproportional valve 71 is held in the totally opened state and the airchamber side solenoid proportional valve 70 is held in the totallyclosed state. Accordingly, while the bag-like member 19 is inflated bythe restoring force of the bag-like member 19 into the inflated state,the air in the atmosphere flows into the bag-like member 19. When thebag-like member 19 is inflated to some extent after the atmospheric airintake period has passed, subsequently, the atmospheric side solenoidproportional valve 71 is held in the totally closed state and the airchamber side solenoid proportional valve 70 is held in the totallyopened state in the pressure-up period. Accordingly, the high-pressureair in the air chamber 69 flows into the bag-like member 19, so that thepressure in the bag-like member 19 will be higher than that of theatmosphere. As a result, the air in the bag-like member 19 is given withpreload like that of the eighth embodiment. Further, after thepressure-up period ends (shortly before the leg 3 on the free leg sideis landed again), the atmospheric side solenoid proportional valve 71 isheld in the totally closed state and the air chamber side solenoidproportional valve 70 is held in the half opened state so as to beprepared for a next landing motion. In this state, the pressure in theair chamber 69 and the pressure in the bag-like member 19 are basicallyequal.

As described above, in the present embodiment, the air in the bag-likemember 19 is given with preload before the landing of the leg 3 as inthe eighth embodiment, so that an acting effect similar to that of theeighth embodiment is achieved. In this situation, particularly in thepresent embodiment, the air pressure source is not needed, andresultingly, the configuration of the landing shock absorbing device 18is simplified and energy consumption of the robot including the landingshock absorbing device 18 may be decreased. In addition, when the airchamber side solenoid proportional valve 70 is in the half opened state,heat generated from the air flowing with the outflow resistance betweenthe air chamber 69 and the bag-like member 19 is released to theatmospheric side when the atmospheric side solenoid proportional valve71 is arranged in the half opened state or the totally opened state, andresultingly, the heat will not continuously be stored up in the landingshook absorbing device 18 of the present embodiment. As a result, aradiator does not need to be provided separately, and this also allowsthe configuration of the landing shock absorbing device 18 to besimplified.

Further, in the landing shock absorbing device 18, to give the preloadto the bag-like member 19 in the inflated state, the preload givingmechanism as described in the ninth embodiment or the tenth embodimentmay also be employed.

Additionally, in the eleventh embodiment, the fluid conduit 68 and theatmospheric side solenoid proportional valve 71 to providecommunications between have the interior of the bag-like member 19 andthe atmospheric side, but these may be eliminated and the air may begiven and received only between the air chamber 69 and the bag-likemember 19. In this case, for example, the air chamber side solenoidproportional valve 70 is maintained in the half opened state.Consequently, in the inflated state of the bag-like member 19, thepressure in the bag-like member 19 becomes high pressure as in theeighth embodiment and the ninth embodiment, resulting in giving thepreload to the air of the interior portion thereof. Therefore, regardingthe reducing of the landing shock, effects similar to those of theeighth embodiment and the ninth embodiment may be obtained. However, theair is sealed in the air chamber 69 and the interior portion of thebag-like member 19, so that heat with the outflow resistance when theair flows between both the components tends to be stored up.Consequently, it is desirable that a radiator or the like is separatelyprovided.

Subsequently, referring to FIG. 18, a twelfth embodiment is described.FIG. 18 is a cross sectional view showing the side face of a footmechanism equipped with a landing shock absorbing device of the presentinvention. Further, the present embodiment differs from those of thefirst and second embodiments only in a partial configuration of the footmechanism and a partial configuration of the landing shock absorbingdevice. Consequently, regarding component portions or function portionsidentical to those of the first and the second embodiments, thereference numerals identical to those of the first and the secondembodiments are used, thereby omitting descriptions thereof.

In the present embodiment, a tube member 13 in a sectional square shapeis fixed on a top face portion of the foot mechanism 6 like those of thefirst and the second embodiments, and an upwardly opened barrel shapebag-like member 19 (variable capacity element) is accommodated in thetube member 13 like the bag-like member of the second embodiment. Inthis situation, a bottom face of the bag-like member 19 is secured to afoot plate member 12 in the tube member 13. In addition, in the tubemember 13, a movable tube member 73 having a bottom is accommodated inthe upper side of the bag-like member 19, and this movable tube member73 is provided in a vertically movable fashion along an innercircumferential surface of the tube member 13. An opened end portion ofthe bag-like member 19 is fixed on the bottom portion of the movabletube member 73. Therefore, the movable tube member 73 is connected tothe foot plate member 12 through the bag-like member 19. Furthermore, aflow passage (a flow-passing hole) 74 as the inflow/outflow means in thepresent embodiment is drilled to be communicated with the interiorportion of the bag-like member 19 on the bottom portion of the movabletube member 73. This flow passage 74 is arranged to be a throttledpassage and constitutes the landing shock absorbing device 18 of thepresent embodiment together with the bag-like member 19.

Additionally, a movable plate 75, which can move in a substantiallyvertical direction along the inner circumferential surface of themovable tube member 73, is accommodated in the interior portion of themovable tube member 73, and the lower peripheral portion of the movableplate 75 is connected to the top face portion of the movable tube member73 through a plurality of elastic members 76 constructed of a elasticmaterial such as spring, rubber or the like (described as springs inFIG. 18). An ankle joint 9 of the leg 3 is connected to the top faceportion of this movable plate 75 through the six-axis force sensor 15.

Further, a space in the interior portion of the movable tube member 73(a space between the movable plate 75) is opened to the atmospheric sidethrough a hole or a gap not shown. Consequently, the interior portion ofthe bag-like member 19 is communicated with the atmospheric side throughthe flow passage 74, and in a state that the bag-like member 18 isinflated as shown, the interior portion of the bag-like member 18 isfilled with the air under the atmospheric pressure. Additionally, in thepresent embodiment, the bag-like member 19 is constructed of an elasticmaterial having difficulty to stretch more than the inflated state(natural state) shown in the figure to prevent the movable tube member73 from falling off from the tube member 13 due to the bag-like member19 stretched by weight of the foot plate member 12, etc. in the landingstate of the leg 3. Alternatively, the movable tube member 73 isstructurally designed to prevent from falling off from the tube member13. Configurations except those just described (including the controlprocessing of the controller 10) are identical to those of the first andthe second embodiments.

In the landing shock absorbing device 18 of the present embodimentconfigured as described above, at the time of the landing motion of theleg 3, when the foot mechanism 6 of the leg 3 makes contact with theground through ground-contacting members 17, the air in the bag-likemember 19 flows out through the flow passage 74 while the bag-likemember 19 is compressed. At this time, the flow passage 74 is athrottled passage, resulting in generating the outflow resistance. Theoperation of the landing shock absorbing device 18 of the presentembodiment like this allows the landing shock at the time of the landingmotion of the leg 3 to be reduced like those of the first and the secondembodiments. Additionally, in the lifting state of the leg 3, thebag-like member 19 is restored into an original inflated state by itselastic force, and at this time, the air in the atmosphere flows intothe bag-like member 19 through the flow passage 74.

Further, in the present embodiment, the bag-like member 19 is providedas a variable capacity element. However, for example, it is possiblethat the tube member 13 is formed in a cylindrical shape (a cylindertube shape) and the movable tube member 73 is formed in a piston shapeto be configured as the variable capacity element in a space under themovable tube member 73 in the tube member 13.

Subsequently, referring to FIG. 19, a thirteenth embodiment of thepresent embodiment is described. FIG. 19 is a cross sectional viewshowing a side face of the substantial portions of a foot mechanismequipped with a landing shock absorbing device of the presentembodiment. Further, the present embodiment differs from the first andthe second embodiments only in a partial configuration of the footmechanism including the landing shock absorbing device, and hence only aconfiguration of the substantial portions of the foot mechanism isdescribed in FIG. 19. Additionally, in the description of the presentembodiment, regarding component portions or function portions identicalto those of the first and the second embodiments, reference numeralsidentical to those of the fist and the second embodiments are used,thereby omitting descriptions thereof.

As shown in FIG. 19, in the landing shock absorbing device 18 of thepresent embodiment, a bag-like member 77 as a variable capacity elementis attached on a bottom face of a foot plate member 12 of the footmechanism 6 in such a manner to substantially cover the entire structureof it. This bag-like member 77 is formed of an elastic material such asrubber or the like into an upwardly opened closed-bottomed containershape, like those of the first and the second embodiments, and theentire periphery of its opened end portion thereof is fixed to aperiphery of a lower face portion of the foot plate member 12. In fourcorners of the bottom face portion of the bag-like member 77 (both theside portions located toward a front portion of the bag-like member 77,and, both the side portions located toward a rear portion thereof),ground-contacting portions 78 corresponding to hard layers 17 b ofground-contacting members 17 in the first and the second embodiments areprovided uniformly with the bag-like member 77. Further, theground-contacting portions 78 may also be separated elements from thebag-like member 77.

Additionally, in an interior portion of the bag-like member 77, a sponge79 (more generally speaking, a soft elastic porous element) isaccommodated in substantially throughout the entire interior portion ofthe bag-like member 77. Moreover, the interior portion of the bag-likemember 77 is communicated with the atmospheric side through a flowpassage 20 drilled in the foot plate member 12 as inflow/outflow meanslike those of the first and the second embodiments. Further, in thepresent embodiment, the ground-contacting members 17 provided in thefirst and the second embodiments are not equipped in the footground-contacting plate 12. Configurations except what has beendescribed (including the control processing of the controller 10) areidentical to those of the first and the second embodiments.

In the landing shock absorbing device 18 of the present embodiment likethis, at the time of the landing motion of the leg 3, the bag-likemember 77 is compressed with the air of its interior and the sponge 79.The air flows out of the bag-like member 77 through the flow passage 20to the atmospheric side, and at this time, the outflow resistance of theair is generated. Consequently, a basic acting effect about reducing thelanding shock is identical to those of the first and the secondembodiments.

On the contrary, in the landing shock absorbing device 18 of the presentembodiment, the sponge 79 is accommodated in the bag-like member 77,resulting in having the following effects. That is to say, when thebag-like member 77 is compressed with the sponge 79, not only thebag-like member 77, but also the sponge 79 has the shape restoringforce, and hence the bag-like member 77 is quickly inflated into thenatural state by lifting the leg 3. Additionally, the sponge 79 isfilled in the bag-like member 77, thereby avoiding a portion of thebag-like member 77 from having an excessive curvature when the bag-likemember 77 is compressed. As a result, a situation that the bag-likemember 77 is broken by the compression may be prevented. Furthermore, inthe compression of the bag-like member 77, when the air in holes of thesponge 79 flow out of the sponge 79, the flow resistance is generated,and resultingly, the damping effect of the landing shock absorbingdevice 18 of the present embodiment may be enhanced. Moreover, soundsgenerated at the time that the air in the bag-like member 77 flows outthrough the flow passage 20 during the compression of the bag-likemember 77 are absorbed by the sponge 79 to some degree, and hence asilencing effect may be obtained.

Further, in the present embodiment, the sponge 79 is adapted to beaccommodated in substantially throughout the interior portion of thebag-like member 77, but the sponge may also be spread and filled at aplurality of regions in the interior portion of the bag-like member 77(for example, four corners of the bag-like members 77). Additionally, inthe interior portion of the bag-like member 19 each provided in thefirst and the second embodiments, a sponge may also be accommodated asin the thirteenth embodiment.

In each embodiment described above, single bag-like members 19, 77 areprovided in the foot mechanisms 6, but a plurality of bag-like membersmay also be provided. For example, as shown in FIG. 20(a) to FIG. 20(d),bag-like members 80 in a shape similar to the bag-like member 19 in thefirst and second embodiments may also be provided in a plurality oflocations on the bottom face side of a foot plate member 12 of a footmechanism (the fourteenth embodiment). Each of FIG. 20(a) to FIG. 20(d)is a model plan view viewed from the bottom face side of the foot platemember 12. Further, in this situation, inflow/outflow means for allowingthe air to flow into and flow out of each bag-like member 80 may beconstructed of a plurality of flow-passing holes drilled in the footplate member 12 to communicate with the interior portion of eachbag-like member 19 (corresponding to the flow passage 20 in the firstand second embodiments), respectively. When a plurality of bag-likemembers are provided in this fashion, in the case that some bag-likemembers 80 of the plurality of bag-like members 80 are compressedaccording to a posture relationship between the foot mechanism and thefloor during the landing motion of the leg, a moment about the axis ofthe horizontal direction is generated in the foot mechanism.Accordingly, the posture control of the foot mechanism by the complianceoperation control functions immediately after any one of the pluralityof the bag-like members 80 makes contact with the ground, andresultingly, an effect of the compliance motion control may be enhanced.

Further, when the plurality of the bag-like members 80 are provided asdescribed above, all of these bag-like members 80 or some of thebag-like members 80 may also be communicated with each other through aflow passage having a throttle or the like. Additionally, for example,the plurality of the bag-like members may also be configured by dividingthe interior portion of the bag-like member in a shape like thethirteenth embodiment with partition walls.

Additionally, a portion of a passage for flowing the air into thebag-like member provided in each embodiment described above (forexample, fluid conduits 34, 41, 46, 53, and 68 in the fifth to theeleventh embodiments) may also be configured by a space in the interiorportion of each leg 3 (including the interior portion of the respectivejoints 7 through 9) or the space in the interior portion of the upperbody 2. This allows the air flowing into the bag-like member to cooldown the actuator and the electric circuit in the interior portion ofthe upper body and each leg 3.

Industrial Applicability

As described above, the present invention is useful to provide a landingshock absorber that can smoothly reduce an impact load during a landingmotion of a leg of a legged mobile robot such as a biped mobile robot ina light-weight configuration.

1. A landing shock absorbing device of a legged mobile robot moving bylifting and landing motions of a plurality of legs that can make contactwith the ground through a ground-contacting face portion of a footmechanism, respectively, comprising: a variable capacity elementprovided in the foot mechanism of each legs each variable capacityelement being compressed by undergoing a floor reaction force during thelanding motion of an associated leg and being inflatable when no longerundergoing the floor reaction force at least by the lifting motion ofthe associated leg, thereby allowing compressible fluid to flow into thevariable capacity element with the inflation thereof and to flow out ofan interior portion of the variable capacity element with thecompression thereof, and an inflow/outflow means for communicating thecompressible fluid into the variable capacity element while inflatingthe variable capacity element in a lifting state of the associated legand for communicating the compressible fluid out of the variablecapacity element with the compression of the variable capacity elementcaused by the floor reaction force, wherein outflow resistance isgenerated during the outflow of the compressible fluid from the variablecapacity element by the inflow/outflow means.
 2. The landing shockabsorbing device of a legged mobile robot according to claim 1, whereinthe variable capacity element is constructed of a deformable bag-likemember provided on a bottom face side of an associated foot mechanism tomake contact with the ground ahead of the ground-contacting face portionof the associated foot mechanism of the associated leg during thelanding motion of said associated leg.
 3. The landing shock absorbingdevice of a legged mobile robot according to claim 2, wherein thebag-like member is constructed by using an elastic material so as toprovide a restoring force toward an inflating direction thereof.
 4. Thelanding shock absorbing device of a legged mobile robot according toclaim 2, wherein each of said variable capacity elements comprise aplurality of the bag-like members.
 5. The landing shock absorbing deviceof a legged mobile robot according to claim 2, wherein a porous element,inflatable together with the bag-like member, is accommodated in aninterior portion of the bag-like member.
 6. The landing shock absorbingdevice of a legged mobile robot according to claim 1, wherein theinflow/outflow means is configured such that inflow resistance of thecompressible fluid into the variable capacity element is lower thanoutflow resistance of the compressible fluid from the variable capacityelement.
 7. The landing shock absorbing device of a legged mobile robotaccording to claim 1, wherein the inflow/outflow means is provided withupper limit pressure limiting means for limiting pressure in thevariable capacity element to be equal to or less than a predeterminedupper limit pressure.
 8. The landing shock absorbing device of a leggedmobile robot according to claim 7, wherein the upper limit pressurelimiting means is disposed such that the upper limit pressure canvariably be adjusted.
 9. The landing shock absorbing device of a leggedmobile robot according to claim 1, wherein the inflow/outflow means isdisposed such that the outflow resistance of the compressible fluid fromthe variable capacity element can variably be adjusted.
 10. The landingshock absorbing device of a legged mobile robot according to claim 1,wherein the inflow/outflow means may direct the compressible fluid outof the variable capacity element and direct the compressible fluid intothe variable capacity element through a common flow passagecommunicating with the variable capacity element.
 11. The landing shockabsorbing device of a legged mobile robot according to claim 1, whereinthe inflow/outflow means is provided with means for increasing pressurein the variable capacity element in an inflated state of the variablecapacity element higher than atmospheric pressure.
 12. The landing shockabsorbing device of a legged mobile robot according to claim 11, furthercomprising means for limiting a capacity of the variable capacityelement in the inflated state to be equal to or less than apredetermined upper limit capacity.
 13. The landing shock absorbingdevice of a legged mobile robot according to claim 1, wherein thecompressible fluid is air and the inflow/outflow means is provided withmeans for directing the air in the variable capacity element out intothe atmosphere when the variable capacity element is compressed, and fordirecting the air from the atmosphere into the variable capacity elementwhen the variable capacity element is inflated.
 14. A landing shockabsorbing device of a legged mobile robot according to claim 1, whereinthe legged mobile robot is a robot in which a position and a posture ofthe foot mechanism are controlled by compliance control so as to allow amoment about an axis in a horizontal direction for the floor reactionforce acting on the foot mechanism of each leg to follow a predetermineddesired moment.
 15. A landing shock absorbing device of a legged mobilerobot according to claim 4, wherein the legged mobile robot is a robotin which a position and a posture of the foot mechanism are controlledby compliance control so as to allow a moment about an axis in ahorizontal direction for the floor reaction force acting on the footmechanism of each leg to follow a predetermined desired moment.